A conventional charging system has been proposed in which a plurality of battery packs are readied for a single electric work vehicle, and when the remaining charge of the installed battery packs runs out, the battery packs are replaced with previously charged battery packs (see Patent Literature 1, for example).
With the charging system disclosed in Patent Literature 1, the remaining charge of the batteries of a plurality of work vehicles is collected, and the expected power consumption until a specific length of time has elapsed is calculated. An index value for determining the battery replacement priority order for the plurality of work vehicles is calculated from the difference between the remaining charge and the expected power consumption, and a return command is issued to work vehicles on the basis of the index value and the allowable charge that can be accepted by the batteries.